1. Ensure you have the favicon hosted either externally or internally in Marketo. (Don't know how to find the link of a image hosted in Marketo? Check this DOC out)

2. On the Landing Page Settings ensure that option 'Remove default favicon links' is selected. Note that this affects all landing pages globally (scroll down in the settings, it might be hiding) [Related DOC]

3. You can specify the favicon in two ways:

a. Directly on the landing page in the custom HTML Header [Related DOC]

b. In the Landing Page Template's Header

4. This code would need to be specified in the header

<link rel="shortcut icon" href="<favicon url>" type="image/x-icon" >

<link rel="icon" href="<favicon url>" type="image/x-icon" >

5. Test the landing page out by either opening it in a different browser or clearing the browser cache and restarting the browser.